Ferguson's two-year audit of Senate expenses, tabled in the upper chamber Tuesday, is forecast to cost $23.6 million when everything is added up.
That's compared with $991,917 in questionable expenses filed by 30 senators that the audit managed to uncover.
Ferguson says there's more to it than a simple dollar-for-dollar comparison.
After all, he says, if it changes attitudes in the upper chamber, it could mean less dicey spending, which will save money down the road.
He also says the Senate has promised more transparency and supervision, and he believes individual senators will be more careful about their spending going forward.
"You can do that comparison just to that amount of money that's identified for the senators, but I think you also need to understand that we have done here has value beyond that," Ferguson said told a news conference Tuesday.
"First of all, I think it is going to result in much more tightening up of the expenses of the senators."
What's more, he added, the public appetite for a thorough examination of the spending habits of senators has been strong in recent years, especially with Mike Duffy in court facing 31 charges of fraud, bribery and breach of trust. Duffy has pleaded not guilty to all counts.
"The public wanted to know what was the case with all of the senators," Ferguson said. "So if we hadn't done this audit, I think people would be asking for such an audit."
Ferguson said he's well aware of the fact the audit was a costly one, but he believes the expense was called for.
"I'm not happy we had to do it, but I am convinced that the audit was necessary."
Note to readers: This is a corrected story. An earlier version said the total amount of questionable spending flagged in the audit was nearly $977,000.
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